[rodjava]

I'm in the final building stages of my datacut hybrid router.

The plans suggest a stepper rated around 400oz. I want to use servos and can get a set of 3 same size 1300oz for the price of 2 servos.

I would use the same motors on all 3 axis's

Do you see any problems with this setup?

Also, the servos I'm looking at are rated 90v. I don't know if this voltage is typical for a home cnc router.

BTW I have pics of my build if anybody is interested.

Rod
San Francisco

[wcarrothers1]

Don't know. I'm running 1200oz servos from camitronics and running them around 36 volts. I don't think under voltage is a problem, might be a bit safer probably will not get max power or acceleration out of them at lower voltage as well.. For example I can only run my x axis at around 200ipm rapids due to speed limits perhaps related to voltage..hehe

But no big deal. They do how ever get heavier as they get bigger. Can't remember how much mine weighed but think they are a good 7-10lbs each. Might be something to think about if your gantry can take the weight.

b/

[Torchhead]

What is the RPM rating of the motors? Typically servos have RPM ratings of 4 to 5 times the steppers. They work better at higher RPM (VS steppers that lose torque with RPM). Normally your gearing needs to change and you can trade the excess RPM of the servo for added torque and resolution.

Do some math. Take the top RPM of your servo at say 70volts and see what that translates to in IPM using your current gearing. Anything over the target rapid speeds of your table is just wasted. You will often find tha you can use smaller servo motors than steppers and get the same speed and torque (and much better resolution).

Typically changing from stepper to servo is not a bolt-on upgrade unless you are willing to leave a lot of potential unused.

There are pro's and Con's for each type of drive. There is no clear defining reasons to do or not do either technology. Statements that steppers are "old" technology and somehow inferior are gross convolutions of truth. Conversely saying that servo's are too complex and wear out sooner have some amounts of truth but should not weigh heavily on the decison.

The bottom line is: How big a load do you need to move and how fast. Secondary consideration is resolution. Servos can still lose position (get noise in your encoder lines and you will see what I mean). The cost is becoming less of a point as well. Usually the cost is for more/bigger power required to run the motors.

We stand agnostic to either approach and try to guide our customer based on the target usage of the machine rather than old-wives-tales (or slick marketing spins).

Tom Caudle
www.CandCNC.com

[rodjava]

Everybody, Please forgive me for my ignorance in the area of electronics. I see myself as a machinist and not a electrical engineer.


My gantry is built mostly of 1" thick tool plate A/L so I'm not worrying about stressing it out. I would be almost impossible. The aproximate weight of the gantry including the router is about 80-100 lbs.

Here are the specs on the servo motors I was interested in. Any advise would be appreciated.

Motor Details:

fficeffice" />> Manufacturer Reliance /ElectroCraft Model E690 Motor Type DC Brush Type Servo Number of Brushes 2 Brush Servicability Externally Replaceable Max Terminal Voltage Volts 90 Maximum Rated Speed RPM 5300 Continuous Torque Oz-in 200 Peak Torque Oz-in 1340 Continuous Current Amperes 10 Peak Current Amperes 80 Max Winding Temp Degrees C 155 Terminal Reistance Ohms 0.3 Armature Inductance mH 1.2 Ke, Back EMF Constant V/kRPM 12.1 Kt, Torque Constant Oz-in/Amp 16.3 Motor Weight (Approx) Lbs 9 Encoder Manufacturer Agilent/HP Encoder Model HEDS-5605 #A06 Encoder Line Count 500 (Yielding 2000 counts/rev) Encoder Channels 2 in Quadrature Encoder Voltage 5 VDC Encoder Current Req'd 75mA >

[rodjava]

Tom,
I just saw your website.
Great! Your RouterPak-3 is what I need.
Unfortunetly, I'm not in a position to buy it at it's current price.
PM me if you would be offering a sale in the near future. This way I can put off
buying the 3 servo's I'm referring to.

Rod

[jalessi]

Hi,

Do you have any more information on the E690 servos, I have three of them and would like to know how to drive them etc...

Thank You

Jeff Alessi
[email protected]

[rodjava]

Jeff,
I never did buy the E690 servos.
Rod

[Torchhead]

Jeff,
I never did buy the E690 servos.
Rod

You wanted to know when the Package Deals were on Special:

Until Feb 30 free shipping on any order over $100.00 (lower 48 states) which saves you 65 to 85 on a package deal. Information is in the CandCNC website in the Specials section (button).

Also we are going to announce a FREE OP-1 Operator Pod for the new Smart Controller we use in the PlazPaks and Router Paks for buyers of the Servo models (2, 3 and 4 extensions on the model #). That special will run for the next 15 orders (about 30 - 45 days).

Tom Caudle
www.CandCNC.com